Food talk: 40-Hz fin whale calls are associated with prey biomass

Animals use varied acoustic signals that play critical roles in their
lives. Understanding the function of these signals may inform about key
life-history processes relevant for conservation. In the case of fin
whales (Balaenoptera physalus), that produce different call types
associated with different behaviours, several hypotheses have emerged
regarding call function, but the topic still remains in its infancy. Here,
we investigate the potential function of two fin whale vocalizations, the
song-forming 20-Hz call and the 40-Hz call, by examining their production
in relation to season, year and prey biomass. Our results showed that the
production of 20-Hz calls was strongly influenced by season, with a clear
peak during the breeding months, and secondarily by year, likely due to
changes in whale abundance. These results support the reproductive
function of the 20-Hz song used as an acoustic display. Conversely, season
and year had no effect on variation in 40-Hz calling rates, but prey
biomass did. This is the first study linking 40-Hz call activity to prey
biomass, supporting the previously suggested food-associated function of
this call. Understanding the functions of animal signals can help
identifying functional habitats and predict the negative effects of human
activities with important implications for conservation.